The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Various engine control algorithms rely on timely estimation of engine speed. The engine control algorithms include direct algorithms, indirect algorithms, and/or diagnostic algorithms. Direct algorithms include determining parameters, such as spark timing, fuel injection volumes, and throttle position. As an example, an indirect algorithm may estimate a parameter, such as engine output torque. Diagnostic algorithms may include, for example, detecting a misfire, detecting operation of a faulty intake or exhaust valve assembly, etc.
An engine control module can obtain estimates of engine speed based on interrupt monitoring of engine speed sensors, such as crankshaft speed sensors. Multiple engine speed sensors are used to accurately detect the position and speed of the crankshaft. The engine control module may condition the signals from the engine speed sensors (e.g., smoothing and filtering) to account for manufacturing variations and noise. Manufacturing variations include variations in distances between engine speed sensors. An engine control system may have, for example, as many as 60 engine speed sensors spaced about a circumference of a monitored gear or toothed wheel. Position and speed of the gear or toothed wheel is directly related to position and speed of, for example, a crankshaft of an engine. This signal conditioning can introduce delay in engine speed determinations.
The position and speed of the crankshaft is affected by back torque exerted on the engine by a transmission. The back torque on the engine can add noise to generated engine speed signals. As a result, additional noise is contained in parameters determined and/or signals generated based on the engine speed signals.